This section is intended to provide a background or context to the disclosed embodiments. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
Wireless communication systems are widely deployed to provide various types of communication content such as voice, data, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., bandwidth and transmit power). Examples of such multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, 3GPP Long Term Evolution (LTE) systems, and orthogonal frequency division multiple access (OFDMA) systems.
Uplink transmitter power control in a mobile communication system balances the need for sufficient energy transmitted per bit to achieve a desired quality-of-service (e.g., data rate and error rate), against the need to minimize interference to other users of the system and to maximize the battery life of the mobile terminal. To accomplish this goal, uplink power control has to adapt to the characteristics of the radio propagation channel, including path loss, shadowing, fast fading and interference from other users in the same cell and adjacent cells.
In LTE Rel-8, which is a single carrier system, the transmit power of the single carrier is limited by the maximum transmit power of the UE. As a result, allocation of power among the various uplink channels and signals (e.g., PUCCH, PUSCH and SRS) is relatively straightforward.
Carrier aggregation (CA) has been proposed for LTE Advanced to aggregate two or more component carriers (CCs) per UE to support wider transmission bandwidths for greater throughput. However, no mechanism has been defined to allocate and control power across multiple uplink component carriers that accounts for the limited transmission power associated with user terminals. In particular, it is an open question as to how to allocate power for competing PUCCH, PUSCH and SRS power commands on multiple component carriers when the transmit power is limited and the power commands in aggregate may exceed the maximum transmit power of a component carrier or the maximum transmit power of the UE.